This is older now and posted before but some may find it interesting to watch the video of this "Marketplace" episode.
Of particular interest would be the part where they hook up a computer to a couple of very oppositely priced brands of HDMI cables. Because you are dealing with data, zeros and ones, it's a pretty simple thing for a computer to monitor the data and show evidently that the data passed through both cables was 100% equal.
Now, are there arguably, total crap HDMI cables? Yes. Certainly there are but crap is crap no matter what you are referring to and that's not the caparison being made.
Marketplace - Packing the Deal. 
